Name: microwave-assisted one-pot synthesis of n-succinimidyl-4-[18f]fluorobenzoate ([18f]sfb)
Uploaded: 2011-06-28T12:00:00
Description: Watch this Scientific Journal Video about Microwave-assisted One-pot Synthesis of N-succinimidyl-4-[18F]fluorobenzoate [18F]SFB at JoVE.com

This study was supported by the US Department of Energy (DE-FG02-09ER09-08 and DE-PS02-09ER09-18), the Jonsson Comprehensive Cancer Center at UCLA, and the Industry-University Cooperative Research Program (UC Discovery Grant, bio07-10665). We thank Dr. Nagichettiar Satyamurthy and staffs at the UCLA Biomedical Cyclotron Facility for providing the F-18 radioisotope and many insightful discussions. We thank Drs. Michael Collins, Greg Leblanc, Joseph Lambert, and Keller Barnhardt from CEM for their technical advice and support. We thank Dirk Williams, Darin Williams, Drs. Joseph Hong Dun Lin, and Michael van Dam for designing and machining parts to modify the CEM microwave reactor and for SPE purification modules.

1. Initial preparations
<ol>
<li>A V-vial (5-mL) RV1 (with stirring bar) is used as the main reaction vessel for performing microwave synthesis. It is connected to a PEEK adaptor with seven inlet/outlet ports connects and placed inside the microwave cavity (see Figure 2). RV2 is connected to SPE cartridge (I) to collect the crude [18F]SFB. RV3 is connected to SPE cartridge (II) for collecting the final [18F]SFB solution. It can be placed in a warm water bath (40&deg;C) to concentrate the correspon...

This simplified three-step, one-pot radiosynthesis of the 18F-acylation reagent [18F]SFB is developed based on non-aqueous chemistry. This process has excellent reproducibility and could be used reliably for the production of [18F]SFB in automated radiochemistry modules, owing to two key modifications described as followings: 1. We employ a deprotection/saponification step in anhydrous KOtBu/DMSO system to replace the common aqueous basic or acidic solution. Our non-aqueous deprotection ...

<table border="1">
<tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments (optional)</td>
 </tr>
 <tr>
 <td>acetic acid in aqueous solution (5%, v/v)</td>
 <td>Fisher </td>
 <td>A38-500 </td>
 <td>Prepared in our lab</td>
 </tr>
 <tr>
 <td>Acetonitrile</td>
 <td>Sigma-Aldrich</td>
 <td>75-05-8</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Diethyl ether </td>
 <td>Sigma-Aldrich</td>
 <td>14775</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Dimethyl Sulfoxide (DMSO)</td>
 <td>Sigma-Aldrich</td>
 <td>472301</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Ethyl 4-(N,N,N-trimethylammonium)benzoate triflate </td>
 <td>Prepared in lab</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (K222)</td>
 <td>Sigma-Aldrich</td>
 <td>29,111-0</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>O-(N-succinimidyl)-N,N,N',N'-tetramethyluronium tetrafluoroborate (TSTU) </td>
 <td>Sigma-Aldrich</td>
 <td>105832-38-0</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Potassium carbonate in aqueous solution (1M)</td>
 <td>Sigma-Aldrich</td>
 <td>209619</td>
 <td>Prepared in our lab</td>
 </tr>
 <tr>
 <td>Potassium tert-butoxide</td>
 <td>Sigma-Aldrich</td>
 <td>156671</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>

microwave-assisted one-pot synthesis of n-succinimidyl-4-[18f]fluorobenzoate ([18f]sfb)

Biomolecules, including peptides,1-9 proteins,10,11 and antibodies and their engineered fragments,12-14 are gaining importance as both potential therapeutics and molecular imaging agents. Notably, when labeled with positron-emitting radioisotopes (e.g., Cu-64, Ga-68, or F-18), they can be used as probes for targeted imaging of many physiological and pathological processes.15-18 Therefore, significant effort has devoted to the synthesis and exploration of 18F-labeled biomolecules. Although there are elegant examples of the direct 18F-labeling of peptides,19-22 the harsh reaction conditions (i.e., organic solvent, extreme pH, high temperature) associated with direct radiofluorination are usually incompatible with fragile protein samples. To date, therefore, the incorporation of radiolabeled prosthetic groups into biomolecules remains the method of choice.23,24
N-Succinimidyl-4-[18F]fluorobenzoate ([18F]SFB),25-37 a Bolton-Hunter type reagent that reacts with the primary amino groups of biomolecules, is a very versatile prosthetic group for the 18F-labeling of a wide spectrum of biological entities, in terms of its evident in vivo stability and high radiolabeling yield. After labeling with [18F]SFB, the resulting [18F]fluorobenzoylated biomolecules could be explored as potential PET tracers for in vivo imaging studies.1 Most [18F]SFB radiosyntheses described in the current literatures require two or even three reactors and multiple purifications by using either solid phase extraction (SPE) or high-performance liquid chromatography (HPLC). Such lengthy processes hamper its routine production and widespread applications in the radiolabeling of biomolecules. Although several module-assisted [18F]SFB syntheses have been reported,29-32, 41-42 they are mainly based on complicated and lengthy procedures using costly commercially-available radiochemistry boxes (Table 1). Therefore, further simplification of the radiosynthesis of [18F]SFB using a low-cost setup would be very beneficial for its adaption to an automated process.
Herein, we report a concise preparation of [18F]SFB, based on a simplified one-pot microwave-assisted synthesis (Figure 1). Our approach does not require purification between steps or any aqueous reagents. In addition, microwave irradiation, which has been used in the syntheses of several PET tracers,38-41 can gives higher RCYs and better selectivity than the corresponding thermal reactions or they provide similar yields in shorter reaction times.38 Most importantly, when labeling biomolecules, the time saved could be diverted to subsequent bioconjugation or PET imaging step.28,43 The novelty of our improved [18F]SFB synthesis is two-fold: (1) the anhydrous deprotection strategy requires no purification of intermediate(s) between each step and (2) the microwave-assisted radiochemical transformations enable the rapid, reliable production of [18F]SFB.

Watch this Scientific Journal Video about Microwave-assisted One-pot Synthesis of N-succinimidyl-4-[18F]fluorobenzoate [18F]SFB at JoVE.com

Microwave-assisted One-pot Synthesis of N-succinimidyl-4-[18F]fluorobenzoate [18F]SFB

A facile, one-pot synthesis of N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) was developed based on a non-aqueous, three-step radiochemical process. Using microwave heating, the entire procedure can be completed in less than 30 min, or 60 min with further purification by preparative HPLC. The decay-corrected radiochemical yields (RCYs) were 35-5% (n > 30).

Microwave-assisted One-pot Synthesis of N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB)

Biomolecules, including peptides,1-9 proteins,10,11 and antibodies and their engineered fragments,12-14 are gaining importance as both potential ...

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